1. Field of the Invention
The present invention relates to a printed circuit board and an inspection method therefor, and more particularly, to a structure suitable for a misregistration inspection of each layer formed on a printed circuit board and an inspection method using the structure.
2. Related Art
A solder resist layer is generally formed on a printed circuit board for the purpose of protecting an outside wiring pattern. Moreover, display printing is applied to the solder resist layer for the purpose of identifying mounting parts.
Both the formation of the solder resist and display printing are performed using a silk screen printing method and printing is performed after conducting registration relative to an NC hole or a circuit pattern formed by etching. A solder resist is often formed by printing photosensitive resin ink, exposing the ink to light through a photomask and developing it.
In this case, misregistration of the solder resist and display printing with respect to a wiring pattern is inspected by observing misregistration check marks using a microscope (e.g., Japanese Utility Model Application Laid-Open No. 60-78156, Japanese Patent Publication No. 2926922).
Examples of electrical inspections are disclosed in Japanese Patent Application Laid-Open No. 5-21923 and Japanese Patent Application Laid-Open No. 2002-158413. Both documents disclose details of silk printing and show that it is possible to electrically inspect whether silk printing has caused misregistration on a wiring pattern or not.
In the case of Japanese Patent Application Laid-Open No. 5-21923, a dot-shaped or ring-shaped silk printing section with which an inspection jig probe (test pin) can come into contact is provided on a mounting pad to decide the presence/absence of misregistration depending on whether the probe contacts the pad or not.
However, the contact caused by a curvature of the probe itself may result in a detection error. A misregistration error of the solder resist is detected more rigorously than silk printing; misregistration of less than 0.1 mm may be regarded as an error and it is difficult to detect the misregistration error only using the probe.
Furthermore, in the case of Japanese Patent Application Laid-Open No. 2002-158413, a silk printing pattern is formed on a circular circuit pattern and exposure of any part of the circuit pattern when silk printing is shifted can be detected using a test pin.
It is also difficult to apply these technical contents to detection of a misregistration error in a solder resist. Another problem is that the test pin used must be of special shape.
In order to solve the above described problems, an object of the present invention is to provide a printed circuit board and an inspection method therefor capable of electrically inspecting display misregistration produced in a solder resist and silk printing with respect to a wiring pattern of the printed circuit board.